Leaded motor fuels



Patented o. 12, 1944 UNITED STATES PATEN OFFICE LEADED MOTOR FUELS Edward C. Shokal, Oakland, Calil'., assignor to Shell Development Company, San Francisco, Calm, a corporation of Delaware No Drawing. Application July 6, 1942,

Serial No. 449,964

8 Claims.

This invention relates to improved motor fuels containing a. tetra-alkyl-lead. More particularly,

my invention relates to tetra-ethyl-lead treated fuels containing as scavengers small amounts of certain tri-halogen alkanes having 2 to 5 carbon atoms.

When fuels containing only tetra-ethyl-lead are burned in an internal combustion engine, a deposit of lead compounds tends to accumulate various parts of the combustion chamber, e. g., the spark plugs, valve stems, etc. This lead may I cause severe deterioration of the effective parts,

resultin in failure of spark plugs, sticking of valves, etc. Scavenger fluids for tetra-ethyl-lead, such as certain halogenated compounds, e. g., alkyl monoor dichlorides or bromides, particularly ethylene dichloride, ethylene dibromide or mixtures of the compounds, are always incor-' porated into leaded fuels. The scavengers reduce lead deposits by releasing halogens during com- Another object is to produce fuel mixtures which contain halogen in amounts not more and preferably less than the stoichiometric equivalent of lead contained in the fuel and which, upon bumlng, still maintain a relatively clean engine. Still bustion which react with the lead to form volatile lead halides which are withdrawn from the combustion chamber with the products of combustion during the exhaust stroke.

The disadvantages of the aforesaid halogenated compounds are that they require a considerable excess of halogen to form, with substantially all of the lead, volatile compounds capable of being eliminated from the combustion chambers during operation of the engines. In the absence of sufficient halogen, lead deposits are formed on the porcelain and the electrodes of spark plugs, which deposits corrode the electrodes and eventually grow to such dimensions that the spark plugs are shorted and rendered useless. On the other hand, excess halogen causes marked corrosion and tends to "chew away metal parts such as sparkplug electrodes, valve seats, valve stems, cylinder walls, etc.

Another disadvantage of the currently used dihalogen compounds is that they boil at temperatures considerably lower than the boiling temperature of tetra-ethyl-lead, as shown by the examples in the table below:

As a consequence, these halogen compounds vaporize farmore rapidly than tetra-ethyl-lead which leads to even greater excess of halogen in another object is to produce fuel mixtures having less tendency to corrode parts of internal combustion engines than leaded gasolines now available.

I have discovered that the above-enumerated objects can be accomplished by combining, in a motor fuel containing lead, a small amount of a chloroor chloro-bromo hydrocarbon containing three halogen atoms and at least two and not more than five carbon atoms. Straight chain hydrocarbons are preferred. It is desirable to use these trihalogen hydrocarbons as the sole scavengers, i. e., not in admixture with those halogen hydrocarbons heretofore employed.

The stoichiometric equivalent as herein defined is the amount of halogen required to combine with lead according to the equation:

. The halogen atoms may be attached to any of the carbon atoms of the hydrocarbons, but preferably are attached to two. adjacent primary and/or secondary carbon atoms as, for example, in the preferred compounds bromo-butane and 2,2,3-tri-chloro butane.

Tri-halogen aliphatic compounds, other than the above butanes, which are useful for my purposes are tri-chloro-ethanes, tri-chloro-propanes, such as 1,2,3-tri-chloro-propane, 1,2,2-tri-chloropropane, 2,3,3 tri chloro propane, etc., trichloro-butanes such as 3,3,4-trl-chloro-butane, 2,3,4-tri-chloro-butane, etc., tri-chloro-pentanes. tri-chloro cyclopentane, corresponding methyl and ethyl substituted tri-chloro-propanes, bu-

tanes and pentanes; mixed-chloro-bromo compounds such as mono-chloro-dibromo-ethanes, propanes, butanes and pentanes, dichloro-monobrpmo-ethanes, propanes, butanes and pentanes of which the following are a few examples: 1,2-

2-chlo'ro-2,3-didichloro 2 bromo propane, 1 chloro 2,3-dibromo propane, 1-chloro-1,2-dibromo-propane, 3-chloro-2,3-dibromo-propane, etc., 3-chloro-3, 4-dibromo-butane, 2-chloro-3,4-dibromo-butane, 2,3-dichloro 3 bromo-butane, 1-chloro-2,3-d1- bromo-2-methyl propane, 1-chlor0-2,3-dibromo cyclopentane, 2-chloro 2,3 dibromopentane, 1- chloro-1,2-dibromo-3-methyl butane.

My compounds may be prepared by any knownresulting mixture was fractionated at reducedpressure. The product, 2-chloro-2,3-dibromobutane was obtained as a liquid which boiled between 74" C. and 78 C. at 20 mm. pressure. The yield. was 88%90% of the theoretical calculated on the basis of bromine.

The amounts of my compounds which operate satisfactorily to supply the scavenging halogen necessary to keep the engine clean are generally those containing between .75 and 1.0 stoichiometric equivalents of halogen per the unit of lead each nm, the combustion chamber was inspected and then the deposit was collected and analyzed. Results were as follows:

Com tion of luel 4 cc. WE. L. per gal.

Condition oi spark plug present in the fuel. I prefer to use an amount of scavenger not in excess of the stolchiometric equivalent, although slightly greater amounts may be used if found necessary under severe engine conditions.

By using less than the stoichiometric equivalent of halogen, less or no.free halogenwill be present in the combustion chamber, and as a result corrosion of many inside parts of the engine is reduced materially. This reduction in corrosion is accomplished without sacrificing lead scavenging efflciency.

The invention is further illustrated by the following example:

Example A sample of a commercial gasoline was divided into five portions. This fuel contained 4 'cc. of tetra-ethyl-lead per gallon. To portion 2 was added 2-chloro-2,3-dibromo-butane in an amount capable of supplying halogen equal to /2 of the stoichiometric equivalent of the lead present. To

portion 3 was added 2-chloro-2,3-dibror no-butane in an amount capable of supplying halogen equal to of the stoichiometric equivalent of the lead present. To portion 4 was added 2-chloro-2,3 dibromo butane in an amount capable of supplying halogen equal to the stoichiometric equivalent of the lead present. To portion 5 was added an amount of Motor Mix- (254 wt.% ethylene dibromide and 74.6 wt.% ethylene dichloride) capable of supplying halogen equal to 1.15 of the stoichiometric equivalent of the lead present. (This amount of Motor Mix is standard in today's commercial automotive fuels containing lead.) Each of the resulting blends was run in a C. F. R. engine for 14 hours. At the end of Porcelain clean, center point in utane.

0.75 theory chloro-dibromob g shape.

Entire spark plug looks like a u e. 1.0 theory chloro-dibromobutane. new one. Commercial Motor Mix (1.15 -Yellow stain on porcelain, center theory halogen). point in good shape. 2

The above data show that the spark plug porcelain condition is better with from roughly 15% to 40% less halogen, when using applicant's compounds, than when using the compounds current- 1! in use.

I claim as my invention:

1. A leaded gasoline containing a compound selected from the group or chloro and chloro-bromo alkanes containing 3 halogen atoms per molecule and at least 2 and not more than 5 carbon atoms the amount of the added halide being suflicient to reduce the deposit of lead compounds formed on combustion of the gasoline.

2. The gasoline of claim 1 wherein the alkane is a straight chain hydrocarbon.

3. A leaded gasoline containing a mono-chlorodi-bromo hydrocarbon containing at least 2 and not more than 5 carbon atoms the amount of the added halide being suillcient to reduce the deposit or lead compounds formed on combustion of the gasoline.

4. A leaded gasoline containing a tri-halogen compound selected from the group of chloro and chloro-bromo alkanes containing at least 2 and not more than. 5 carbon atoms, two of which halogen atoms are attached to the same carbon atom the amount of the added halide being sufflcient to reduce the deposit of lead compounds formed on combustion of the gasoline.

5. A leaded gasoline containing a tri-halogen compound selected from the group of chloro and chloro-bromo alkanes containing at least 2 and not more than 5 carbon atoms, said halogens being attached to two adjacent carbon atoms the amount of the added halide being sumcient to reduce the deposit or lead compounds formed on combustion of the gasoline.

6. A leaded gasoline containing 2-ch1oro-2,3- dibromo-butane the amount of the added halide being suflicient to reduce the deposit of lead compounds formed on combustion of the gasoline.

7. A leaded gasoline containing 2,2,3-trichloro-butane the amount of the added halide being suiiicient to reduce the deposit of lead compounds formed on combustion of the gasoline.

8. A leaded gasoline containing an amount of a compound selected from the group of chloro and chloro-bromo alkanes containing 3 v halogen atoms per molecule and at least 2 and not more than 5 carbon atoms, said amount containing halogen in quantities equal to between ."15 and 1.0 stoichiometric equivalents of the lead contained in said gasoline.

EDWARD C. SHOKAL. 

